Instead of atoms, individual nanoparticles are linked to one another in the new nanoparticles. Image: Science
Read aloud Scientists at the Massachusetts Institute of Technology (MIT) at Cambridge have developed a method for making long chains of metal nanoparticles. Adjacent particles are bound together by short molecular chains attached to the poles of the particles. The researchers believe that such chains can be used, among other things, to improve the mechanical properties of glasses. The trick of the method conceived by Francesco Stellacci and his colleagues is to form two opposing poles on the surface of tiny fractions of a micron of small gold particles. To accomplish this, the particles were coated with a one-molecular layer of an organic molecule. The molecular chains were attached to the gold atoms in densely packed form by means of sulfur bridges.

The researchers were able to show that in this way two defect sites were formed on opposite poles of the particles, on which no molecules could be fixed. According to Stellacci, this is a necessary consequence of the topology of a tightly packed arrangement of long molecular chains on a spherical surface.

The coated gold particles thus somewhat resembled chemical molecules with exactly two binding sites each. In fact, the researchers actually succeeded in combining the gold particles into chains by means of short bridge molecules in a further chemical reaction: the connecting pieces could fit precisely into the defects at the poles of the particles.

According to Stellacci, chain formation corresponds to the polymerization reaction in the formation of plastics from individual monomer molecules. The longest of the gold chains produced by the researchers contained about 50, 000 individual beads. Scientists now want to increase the length of these chains, called "nanoplastics", by several orders of magnitude and then incorporate them into materials such as glasses. The aim is to set in this way their mechanical, electrical and optical properties as desired. display

Gretchen DeVries (MIT) et al .: Science, Vol. 315, p. 348 Stefan Maier

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